The retention of a urinary catheter in a human bladder so as to prevent it from slipping out during the period required to drain the bladder has been accomplished in several ways. The generally accepted so-called "Foley catheter" has a small inflatable balloon at its distal end (the end which is inserted) which is inflated to hold the distal end inside the bladder after the distal end has been inserted safely through the urethra and into the bladder. Inflation is accomplished by pumping a fluid into the balloon through an inflation lumen, a passage in the shaft of the catheter parallel to the drainage lumen or passage. The inflation fluid may be a gas or a liquid such as distilled water.
Current methods of inflating the balloon are susceptible to over- or under-inflation. Methods and devices for inserting the catheter and inflating the balloon are cumbersome and complicated. For instance, one such procedure is to insert the distal end of the catheter through the urethra into the bladder and at the same time to insert a syringe needle into the inflation lumen and then squeeze the syringe to inflate the balloon. This may require an operator and an assistant and may result in trauma to the patient if the balloon is inadvertently inflated while it is still within the urethra.
With any Foley catheter, means also have to be provided for deflating the retention balloon after use. Again, the deflation systems in present use are sometimes too complicated. This is often the case when the inflating device is a syringe and needle inserted into the inflation lumen. Deflation will again require such insertion of the syringe to withdraw the fluid. This may also be a two-handed operation, requiring a second person to hold the catheter.
So-called self-inflating catheters were developed to try to solve these problems, but they have had problems of their own. A number of arrangements have been tried to provide a reservoir, integral with the catheter, for storage of inflation fluid under pressure ready to be expelled to inflate the retention balloon. But such systems have not thus far met the requirements for satisfactory performance.
Such requirements are that the catheter have a long shelf-life under sanitary conditions, that it be immediately ready for use, that it be simple to operate by one person and that it be inexpensive to produce as a throwaway item. Its arrangement must also be such that the retention balloon is capable of deflation and reinflation if the instrument is prematurely inflated before its desired placement with the distal end in the bladder.
A widely used type of self-inflating catheter has an over-inflated rubber reservoir in which the fluid is retained by a clamp under pressure during storage. After insertion of the catheter into the bladder, the clamp is removed to inflate the retention balloon. During storage, however, the stretched reservoir walls tend to lose their restoring force because they "take a set" and "lose memory" so that when the clamp is removed, the rubber reservoir does not exert enough force to inflate the balloon. Also, once such a system is activated to inflate the retention balloon, there is no way of deflating and reinflating the balloon in case the catheter is not properly placed in the first instance. There is also no adequate way of determining how much of the fluid has been dispersed from the reservoir at any instant. Another problem is that when the fluid is thus stored under pressure, considerable loss of fluid occurs through the stretched reservoir walls during storage. This reduces the amount by which the retention balloon may be inflated, and in some cases so much fluid is lost that no inflation occurs in use.
The principal objects of this invention are therefore to provide in an inexpensive urinary catheter a retention balloon inflation system in which no fluid loss occurs, which will allow the retention balloon to be deflated and reinflated and which will provide a visual indicator of the degree of inflation at any instant.